DE3127821A1 - FIXED PROTON LADDER AND THEIR USE - Google Patents

Description

-A-

The invention relates to solid proton conductors and their use.

Proton-conducting solid materials have already become known, such as molybdophosphoric acid and tungstophosphoric acid (H-PW .. "0.'nH_O), hydrogenuranyl phosphate (HUO ₂ PO ₄ - 4H ₂ O) and hydrous ß-aluminum oxide (WA England et al., Solid State Ionics 1 (1980) 231-249 and PE Childs et al., Journal of Power Sources 3 (1978) 105-114) It has also been described that aluminosilicates, for example zeolites, are also ion conductors (MS Wittingham et al. , Proceedings of the 7th International Symposium on the Reactivity of Solids, Bristol (July 17-21, 1972) 125-139). These publications also state that certain solid proton conductors, such as hydrogenuranyl phosphate tetrahydrate, can be used as separators for primary and secondary electrochemical cells, ie batteries (PE Childs et al., Loc. Cit.).

From CM. Johnson et al. was recently reported (International Conference on Fast Ionic Transport in Solids, Gattlingburgh, Tennessee (May 18-22, 1981) reported that H-Zeoli— the have a proton conductivity that, if one

- 4 - 1 - 1 wet compacts are inserted, 3 χ 10 0hm - cm at 20 ° C amounts to. It is stated that this proton conductivity is greatest when there is more water than the crystal lattice channels, i.e. when the material is wet. It is also emphasized that the conductivity is very low for the dry material and increases with increasing amount of water, with found becomes that the mechanism of proton conduction is a guiding process of the Grotthus type (see W.A. England et al.,

loc. cit.) · This is consistent with the fact that the proton conductivity decreases with increasing drying, i.e. apparently in the liquid phase, as with a conventional one liquid ion conductor takes place.

For the production of primary cells or secondary cells and electronic components, it is often necessary to introduce electrolytes between electrodes. The liquid electrolytes normally used are disadvantageous because they cannot easily be designed as self-supporting structures and often give rise to corrosion problems. The previously known solid proton conductors react like a Br ^ nsted acid and are therefore only stable with a limited number of electrode materials, but not with base metals such as zinc, aluminum, iron and the like, which are often used for electrochemical cells. Furthermore, some of the previously known solid proton conductors are very sensitive to reduction, such as the above-mentioned _{molybdophosphoric acid or tungstophosphoric acid (H 3} X "PO. ■ 29H ₂ O, (H ₃ O) ClO", where X stands for molybdenum or tungsten). Some materials are radioactive or contain toxic heavy metal cations

(HgUO ₂ JO ₆ -4H ₃ O, Sb ₃ O ₅ - 4H ₂ O, SnO ₂ - 2.3H ₂ O etc.) 25

With the exception of the proton-conducting ß-aluminum oxide All materials give water even at low temperatures with a considerable reduction in volume so that it is not possible to apply thin layers by vapor deposition, sputtering or the like. Farther sintering of the materials above the dewatering temperature is not possible. The previously known solid Proton conductors thus contain either expensive or dangerous elements or are difficult to manufacture.

len. With the exception of ß-alumina, all materials are extremely soft. In addition, most of the previously known solid proton conductors are only two-dimensional Proton conductors, which consequently have anisotropy properties show that are important for their application (for example with regard to the mechanical Stability). In addition, most conventional solid proton conductors suffer from being a have insufficient conductivity (see M.S. Wittingham et al., loc. cit.).

The object of the present invention is now to provide solid proton conductors that are also in the dry state have a high conductivity, which can be produced easily and cheaply and which results in excellent Dimensions are particularly suitable as separator material for a wide variety of electrochemical purposes.

This task is now solved by the solid proton conductor according to the main claim. The subclaims relate to particularly preferred embodiments of this subject matter of the invention and the use of these solid proton conductors.

It has surprisingly been found that proton-containing Zeolites containing cations, the six-membered rings and larger rings as secondary assemblies of the zeolite Have structure, even in the presence of a purely zeolitic phase, such as zeolitic water, a high one Achieve proton conductivity. This has the considerable advantage (preferably with the basic NH.-zeolites) that there are no corrosion problems materials in contact with these solid proton conductors occur, so that it is possible to use batteries

or other electrochemical cells with significantly longer lifetimes using these solid ones Manufacture proton conductors as separator materials.

The invention therefore relates to solid proton conductors which are characterized by proton-containing cations exhibiting zeolites with six rings and / or larger rings as secondary assemblies of the zeolite Structure in whose crystal lattice channels a phase favoring proton transport (preferably a polar phase) is present. It is about open structures (host lattice), which are predominantly made of silicon dioxide and / or aluminum oxide and which contain a sublattice of the proton-conducting cations in which the phase promoting proton transport is present, which has a diffusion coefficient of at least

- 15 2 -1

10 cm ■ s must have. At least a certain part of the sublattice behaves like a Βτφη- sted base in relation to the host lattice.

Regarding the definition of the secondary assemblies, R.M. Barrer "Zeolithes and Clay Minerals as Sorbents at Molecular Sieves ", Academic Press London, New York, San Francisco (1978) and F. Schwocho et al." Zeolite production, Structure, Application ", Angewandte Chemie, Volume 87 (1975) No. 18, pages 659-667. In these publications it is stated that the structure of the various structure types of the zeolite lattice can be determined best described with the help of eight secondary assemblies can, the four-rings (4), six-rings (6), eight-rings (8), double four-rings (4-4), double six-rings (6-6) and complex or multiple units (4-1, 5-1, 4-4-1) include.

It has now been shown that zeolites whose zeolite lattice structure is six-membered are suitable according to the invention and / or larger rings as secondary assemblies, as is particularly the case with the zeolites of the analcime group, the Chabazite group, the Phillipsite group and / or the Faujasite group applies. Zeolites which are particularly preferred according to the invention are the hydrated forms of analcime, zeolite L, sodalite, phillipsite, gismondine, zeolite A, zeolite X, zeolite Y, zeolite ZK-5 and zeolite omega.

The proton conductors preferred according to the invention with the Secondary assemblies of the zeolites contained are summarized in the following table.

14th K-Analcime · nL ⁺ 6th 8th 4-4 6-6 4-1 5-1 4-4-1 K-Phillipsite · nL
K-Gismondin · nL ⁺ K-Zeolite Omega · nL
K-zeolite L-nL
K-sodalite nL ⁺ K-zeolite T-nL
K-zeolite Y-nL
K-zeolite A-nL
K-zeolite ZK-5-nL + ^{+ +}

κ = NH. ⁺ , N ₃ H ₅ ⁺ , H ⁺ -AmIn or HO ⁺ (besides other cations or

exclusively) L = H _? 0 or low molecular weight aliphatic or cyclo-

aliphatic alcohol with no more than 6 carbon atoms.

The solid proton conductors according to the invention contain Now a mobile phase in the crystal lattice channels of the zeolite, namely the one that promotes proton transport Phase, the amount of which is preferably less than the amount necessary to fill in for the mobile Phase accessible crystal lattice channels of the zeolitic structure is required. It has been shown that that a surprisingly much higher conductivity can already be achieved, if not, as before suppose more than the amount of a phase necessary to fill the grid channels, for example Water is present. According to a preferred embodiment of the invention, the one which promotes proton transport is Phase in a to the formation of a monomolecular layer on the crystallite surfaces of the Sufficient amount of zeolite. According to the invention, this can be achieved by converting the into the ammonium form transferred zeolite at temperatures of 500 to 600 ° C, optionally sintered in vacuo and then brings it back into equilibrium with the phase favoring proton transport.

The solid proton conductors according to the invention contain proton-containing cations based on preferably ammonia, hydrazine or cations of an organic Amine, preferably a low molecular weight aliphatic, cycloaliphatic or aromatic amine with 1 up to 6 carbon atoms, such as methylamine, ethylamine or pyridine; and as promoting proton transport Phase preferably a polar phase, more preferably water and / or alcohol. Particularly preferred than the den

In addition to water, the phase favoring proton transport is the low molecular weight aliphatic alcohols with 1 up to 6 hydrocarbon atoms, preferably methanol or ethanol. According to the invention it is possible to use the phases promoting proton transport individually or to be used in combination. According to the invention, a combination of ammonium ions is particularly preferred proton-containing cation and water as the proton transport favoring phase.

It is known that zeolites are ion exchangers, so that a number of cations or cation combinations are incorporated into the crystal structure, as are protons, which as such are not mobile in these lattice structures, but are firmly bound to the oxygen atoms with the formation of hydroxyl ions. However, if, according to the invention, a basic phase, such as ammonia, methylamine, etc., is introduced into the crystal lattice channels in addition to the host lattice, it becomes possible to bind the protons to this phase as proton-containing cations and in this way depending on the diffusion coefficient of the basic Transport phase. In the solid proton conductors according to the invention, proton conduction thus takes place via a translational movement of proton-containing cations ("vehicle mechanism"), such as H ₃ O ⁺ , NH ₄ ⁺ , N ₃ H ₅ ⁺ , H ⁺ -pyridine, CH ₃ NH ₃ ^+, etc. , which can be thought of as composed of the basic phase used to form the proton-containing cation, water, ammonia, hydrazine, pyridine, methylamine, etc., and the protein (H) transported by this. If the basic phase is much smaller than the crystal lattice channels of the zeolite, the mobility can be very low. According to the invention, however, it can be achieved by adding a further phase, namely

the phase promoting proton transport, for example water or an alcohol such as methanol,
Ethanol etc. can be increased considerably. In this
According to the invention, it is possible to create solid proton conductors

to form a proton conduction at room temperature

- 3 - 1 - 1
greater than 10 ohm cm.

It has also been shown that the invention solid proton conductor because of their very low

Due to their water content and their basic behavior, there are no corrosion problems with those in contact with them
Raise electrodes so that they stand out
Dimensions as separator material or electrolyte for primary
or secondary electrochemical cells, fuel cells, electrolysis cells, electrochromic displays, electronic storage elements (such as timers, memory elements, etc.)
and the like. In particular, they can be used with advantage where, in addition to a high proton conductivity, a high diffusion coefficient of water is necessary, for example for metal / air cells. The invention therefore also relates to the use of the solid proton conductors according to the invention according to claim 12.

The following example serves to further explain the invention.

example

5 g of a type A zeolite of approximate
Composition Na ₄ Ca-Al ₁₂ Si ₁ -O (pseudocubic a =
1.242 nm, Linde molecular sieve 5 A) in 250 ml of an aqueous saturated ammonium carbonate solution. In the course of an exothermic reaction, with constant stirring

about 50% of the sodium ions are exchanged for ammonium ions overnight and about 14.5% by weight of water are taken up. The reaction product (of the approximate composition (NH ₄ I ₂ Na ₂ Ca Al ₂ Si ₁₂ 0. "- nH ₂ O) is filtered off, dried in the air and stored over water at room temperature. The material has a room temperature.

- 3-1-1

conductivity of 2 χ 10 Ohm · cm and can be Press very well in excess of water, alcohol or the like.

The material can be ^{sintered at 300 °} C. with the release of water. If an equilibrium is established over water at room temperature, the proton conductivity of the starting material is restored.

If the material ^{is sintered at 600 °} C. with the release of water and ammonia, relatively abrasion-resistant sintered bodies are obtained, which are mechanically far more stable than the bodies produced ^{by sintering at 300 ° C.} _{Thin layers (e.g. MoO 3} AWO etc.) can now be applied to the sintered body non-destructively by vapor deposition, sputtering etc. The equilibrium division over an ammonia solution at room temperature leads again to the proton conductivity of the starting material. In this way, disks (with a diameter of 25 mm and a thickness of 1 mm) are obtained which have a reproducible electrolyte resistance of 11 ohms.

If you use these discs together with a pair of electrodes made of manganese dioxide (with a graphite content of 8%) and iron, a cell with a cell voltage is obtained from 0.7 to 1.2 volts and a short-circuit current of 60 / UA, which is reversible and operates for very long periods of time with little voltage loss permit.

Using the measures given above, but using methylamine, methanol or ethanol and using other zeolite host lattices the following proton conductors are obtained.

_ _ ι - 1 - sigma / Ohm cm _ / wt .-%

NH ₄ -analcium η H ₂ O 2 χ 10 ~ ⁴

NH ₄ philipsite · nH ₂ 0 7 χ 10 ⁵ 20

NH ₄ -Gismondin η H ₂ O 8 χ 10 ~ ⁵ 16

NH ₄ Sodalite · η H ₃ O 2 χ 10 ~ ⁴ 24.5

NH ₄ zeolite L- η H ₃ O 5 χ 10 * ° 13.5

NH ₄ -zeolite Omega η H ₂ O 2 χ 10 ~ ⁴ 24

NH ₄ zeolite Α η H ₃ O 2 χ 10 ~ 14.5

CH ₃ NH ₃ zeolite A -n H ₂ O 7 χ 10 ⁵ 13.5

-4

NH ₄ zeolite A- η CH ₃ OH 1.3 x 10

NH ₄ ~ zeolite A- η C ₂ H ₅ OH 1.5 χ 10 ~

NH.-zeolite X ■ η H ₂ O 1 χ 10 -3 2

NH ₄ zeolite Y. η H ₃ O 1 χ 10 ~ ³ 31

NH ₄ zeolite ZK-5 8 χ 10 ~ ⁴ 15

H-zeolite A · η HO 6 χ 10 ~ ⁷ 13.5

Claims (12)

Patent attorneys Dipl.-Ing. H. Veickmahn, Dipl.-Fms. Dr. K. Fincke Dipl.-Ing. F. A. Weickmann, Dipl.-Chem. B. Huber Dr. Ing.H. Liska 8000 MÜNCHEN 86, DEN f & POSTFACH S60 820 MÖHLSTRASSE 22, CALL NUMBER 98 39 21/22 HtM / kÜ MAX-PLANCK-GESELLSCHAFT FOR THE PROMOTION OF SCIENCE e.V. Bunsenstrasse 10, 3400 Göttingen, Germany 1. Fixed proton conductors, characterized by zeolites having proton-containing cations with six rings and / or
larger rings as secondary assemblies of the zeolitic structure, in whose crystal lattice channels a phase that promotes proton transport is present. 2. Proton conductor according to claim 1, characterized in that the phase promoting proton transport is polar
Phase is. 3. proton conductor according to claim 1 or 2, characterized in that the proton transport promoting phase in a Amount is present, which beyond the filling of the lattice channels to the formation of a monomolecular Layer on the crystal surfaces is sufficient. 4. proton conductor according to claim 1 or 2, characterized, that the proton transport favoring phase in a Amount is present which is less than that for filling the crystal lattice channels accessible for this phase the zeolitic structure required amount. 5. proton conductor according to claims 1 to 4, characterized in that the phase favoring proton transport is a diffusion having. -15 2 -1 Diffusion coefficients of at least 10 cm · s 6. Proton conductor according to claims 1 to 5, characterized in that the zeolite has as proton-containing cations ammonium cations (NH.), Hydronium cations (H-.0), hydrazinium cations (NH ₁ -) or organic amine cations. 7. proton conductor according to claim 6, characterized in that the organic amine cation is a cation based of at least one low molecular weight aliphatic, cycloaliphatic or aromatic amine with 1 to 6 carbon atoms, preferably of methylamine, ethyl amine or is pyridine. 8. proton conductor according to claims 1 to 7,
characterized in that the zeolite contains water and / or an alcohol as the phase promoting proton transport. 9. proton conductor according to claim 8, characterized in that the zeolite is at least one low molecular weight alcohol contains aliphatic alcohol with 1 to 6 carbon atoms, preferably methanol or ethanol. 10. proton conductor according to claim 1 to 9,
characterized in that the zeolite is a zeolite of the analcime group, the chabazite group, the phillipsite group and / or faujasite group. 11. Proton conductor according to claim 10,
characterized in that it contains as zeolite analcime, zeolite L, sodalite, phillipsite, gismondine, zeolite A, zeolite X, zeolite Y, zeolite ZK-5 and / or zeolite omega. 12. Use of the solid proton conductor according to the claims 1 to 11 as separator material or electrolyte for primary and secondary electrochemical cells, fuel cells, Electrolysis cells, electrochromic displays and electronic storage elements.